PROJECT SUMMARY/ABSTRACT Emergency General Surgery (EGS) constitutes a significant public health burden in the United States. With approximately 3 million admissions a year, this subset of high-risk surgical conditions accounts for 50% of all surgical mortality, despite representing only 11% of surgical admissions. Timely access and presentation to facilities capable of rapid surgical intervention is critical for these conditions, as delays in care are associated with increased morbidity and mortality. Previous research in EGS has identified rural, minority, uninsured and socioeconomically disadvantaged populations as having higher rates of advanced clinical presentation and worse EGS outcomes, raising concerns for disparities in access to emergency surgical services. While it is intuitive that geographic access to care plays a role in EGS outcomes, it is unclear to what degree it interacts with the above socio-demographic factors and contributes to these disparities. The overarching goal of this proposal is to understand the etiology of disparities in access to EGS. Our central hypothesis is that geographic access contributes to EGS outcomes through interactions with social, patient and disease-related factors in a manner which disproportionately affects vulnerable populations. We will address these hypotheses through the following Specific Aims: (1) We will first develop a national geographic information system to quantify disparities in access to EGS services. Using national census and hospital data, we will generate an interactive map of EGS-capable hospitals, and layer this with distributions of key populations of interest: rural, minority, uninsured and low-income individuals. We will then use advanced spatial modelling techniques to quantify disparities in access to EGS hospitals for these populations and identify regions in greatest need of enhanced surgical capacity. (2) Subsequently, we will combine clinical data with spatial models to determine the contribution of geographic access to disparities in EGS outcomes. Using mixed-effects regression modelling, we will evaluate to what extent improving geographic access would reduce the observed outcome disparities for vulnerable populations. The proposed research represents a novel application of GIS technology to surgical research. The use of geospatial modelling will provide important insight into how geographic access and resource distribution contribute to surgical disparities for time-sensitive EGS conditions. This approach will further enable us to identify specific regions and populations to target for intervention. Finally, the development of a national GIS platform holds potential to inform future EGS regionalization and planning efforts by ensuring equitable distribution of services for vulnerable populations.